The first bit is simple. It's not fire, it's fatal.
The danger is not smoke and flames, but the death of someone.
(Connect the FB to an AC supply and if somebody dies.... I don't think I need say more. But now that I have, FB have little choice....)
The second part explains methods of dimming AC circuits. Simple & ancient. Used for tungstens, fluoros, motors etc.
Seek and ye shall find.